Just received some 1/2 x 20 bolts for my used, ebay Paughco's (3" coke bottle style), but found out the risers are 1/2x13 standard! Does anyone know if Paughco ever use 1/2x13 for their riser threads? The risers are steel, passed the magnet test, but am wondering why the thread size is wrong. Anyone else make steel chrome risers like that? Being chromed steel, I'd imagine they're not an Asian knock-off, but who knows!

 

That is a coarse thread common bolt.
fine thread would be 1/2x 20